Abstract
We have obtained CCD UBVRI photometry of 3620 stars in the globular cluster NGC 6723, one of the few globular clusters with a horizontal branch well- populated on both sides of the instability strip. This is the rst deep ve-color study of NGC 6723. We have de- termined several important parameters for this cluster. Its color excess is E(B V )=0 :110:01. The most plausible value of metallicity is (Fe=H) = 1:22 0:15; even lower values are possible. The apparent distance modulus of the cluster is (m M )V;6723 =1 4 :76. From isochrone analysis, we prefer the NGC 6723 age in the range between 15 and 16 Gyr, in the scale of Bergbusch & VandenBerg (1992). We nd a close similarity of the shape and slope of the red giant branch in NGC 6723 and M 3 and of the mag- nitude dierence between the main-sequence turno and the horizontal branch in NGC 6723, M 3, and M 5.
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